The Polish government is moving to rein in demands by ruling-party politicians who want to pursue compensation from Germany for damages during World War II.

Calls for reparations from the 1939-1945 conflict, during which about 6 million Poles — half of them Jews — were killed, are souring ties between the European Union's largest eastern member and Germany, the bloc's paymaster. Ruling-party officials have linked the Nazi invasion to Poland's moral right to receive aid from Brussels after the E.U. threatened sanctions against the country of 38 million for flouting the bloc's democratic standards.

Successive Polish governments have declared the issue of wartime damages from Germany closed, and that "hasn't changed," Deputy Foreign Minister Marek Magierowski said in a statement published on parliament's website. "Further analysis is required to gain an effective way to pursue reparation claims."

Deputy Prime Minister Mateusz Morawiecki lamented this month that Poland was "massacred" by the country's neighbor during the war and the "historic bills have not been settled," echoing comments by ruling party leader Jaroslaw Kaczynski.

Unlike western European nations that settled World War II claims in the decades after the bloodiest conflict in history, Poland signed its postwar border treaty with Germany only in 1990, a year after the collapse of communism and the Berlin Wall. As part of the Soviet bloc, Poland didn't take part in the U.S.-funded Marshall Plan that helped rebuild western Europe.

The dispute comes amid increasing isolation of the Polish government within the E.U. and pits the biggest net beneficiary of the bloc's 140 billion-euro ($164 billion) annual budget against its main economic partner. Polish trade with Germany amounts to more than $100 billion a year — more than a quarter of imports and exports and more than the next five countries combined.

A lawmaker from Kaczynski's Law & Justice Party asked two weeks ago for a parliamentary analysis on whether Poland has grounds to seek damages from Germany, suggesting that a 1953 declaration by the nation's communist authorities was not a sovereign decision but one made instead by a puppet regime of the Soviet Union.

The one-sided 1953 declaration was made "in accord with the constitutional order of that era, and potential pressure from the Soviet Union can't be recognized as a threat of the use of force breaching international law," Magierowski said, citing a Polish government statement from 2004.

Subsequent arrangements between the two nations, which among other issues gave Poles the right to participate in compensation funds set aside for victims of forced-labor camps, include a clause that bars Poland from pursuing further Nazi-era claims, Magierowski said.

However, the Polish government can still engage in talks with Germany about increasing "humanitarian provisions" for still-living victims of the Nazi regime, he said.